-
Notifications
You must be signed in to change notification settings - Fork 24.8k
/
async_pipe.ts
153 lines (129 loc) · 4.6 KB
/
async_pipe.ts
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
/**
* @license
* Copyright Google LLC All Rights Reserved.
*
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.io/license
*/
import {ChangeDetectorRef, EventEmitter, OnDestroy, Pipe, PipeTransform, ɵisPromise, ɵisSubscribable} from '@angular/core';
import {Observable, Subscribable, Unsubscribable} from 'rxjs';
import {invalidPipeArgumentError} from './invalid_pipe_argument_error';
interface SubscriptionStrategy {
createSubscription(async: Subscribable<any>|Promise<any>, updateLatestValue: any): Unsubscribable
|Promise<any>;
dispose(subscription: Unsubscribable|Promise<any>): void;
onDestroy(subscription: Unsubscribable|Promise<any>): void;
}
class SubscribableStrategy implements SubscriptionStrategy {
createSubscription(async: Subscribable<any>, updateLatestValue: any): Unsubscribable {
return async.subscribe({
next: updateLatestValue,
error: (e: any) => {
throw e;
}
});
}
dispose(subscription: Unsubscribable): void {
subscription.unsubscribe();
}
onDestroy(subscription: Unsubscribable): void {
subscription.unsubscribe();
}
}
class PromiseStrategy implements SubscriptionStrategy {
createSubscription(async: Promise<any>, updateLatestValue: (v: any) => any): Promise<any> {
return async.then(updateLatestValue, e => {
throw e;
});
}
dispose(subscription: Promise<any>): void {}
onDestroy(subscription: Promise<any>): void {}
}
const _promiseStrategy = new PromiseStrategy();
const _subscribableStrategy = new SubscribableStrategy();
/**
* @ngModule CommonModule
* @description
*
* Unwraps a value from an asynchronous primitive.
*
* The `async` pipe subscribes to an `Observable` or `Promise` and returns the latest value it has
* emitted. When a new value is emitted, the `async` pipe marks the component to be checked for
* changes. When the component gets destroyed, the `async` pipe unsubscribes automatically to avoid
* potential memory leaks.
*
* @usageNotes
*
* ### Examples
*
* This example binds a `Promise` to the view. Clicking the `Resolve` button resolves the
* promise.
*
* {@example common/pipes/ts/async_pipe.ts region='AsyncPipePromise'}
*
* It's also possible to use `async` with Observables. The example below binds the `time` Observable
* to the view. The Observable continuously updates the view with the current time.
*
* {@example common/pipes/ts/async_pipe.ts region='AsyncPipeObservable'}
*
* @publicApi
*/
@Pipe({name: 'async', pure: false})
export class AsyncPipe implements OnDestroy, PipeTransform {
private _latestValue: any = null;
private _subscription: Unsubscribable|Promise<any>|null = null;
private _obj: Subscribable<any>|Promise<any>|EventEmitter<any>|null = null;
private _strategy: SubscriptionStrategy = null!;
constructor(private _ref: ChangeDetectorRef) {}
ngOnDestroy(): void {
if (this._subscription) {
this._dispose();
}
}
// NOTE(@benlesh): Because Observable has deprecated a few call patterns for `subscribe`,
// TypeScript has a hard time matching Observable to Subscribable, for more information
// see https://github.com/microsoft/TypeScript/issues/43643
transform<T>(obj: Observable<T>|Subscribable<T>|Promise<T>): T|null;
transform<T>(obj: null|undefined): null;
transform<T>(obj: Observable<T>|Subscribable<T>|Promise<T>|null|undefined): T|null;
transform<T>(obj: Observable<T>|Subscribable<T>|Promise<T>|null|undefined): T|null {
if (!this._obj) {
if (obj) {
this._subscribe(obj);
}
return this._latestValue;
}
if (obj !== this._obj) {
this._dispose();
return this.transform(obj);
}
return this._latestValue;
}
private _subscribe(obj: Subscribable<any>|Promise<any>|EventEmitter<any>): void {
this._obj = obj;
this._strategy = this._selectStrategy(obj);
this._subscription = this._strategy.createSubscription(
obj, (value: Object) => this._updateLatestValue(obj, value));
}
private _selectStrategy(obj: Subscribable<any>|Promise<any>|EventEmitter<any>): any {
if (ɵisPromise(obj)) {
return _promiseStrategy;
}
if (ɵisSubscribable(obj)) {
return _subscribableStrategy;
}
throw invalidPipeArgumentError(AsyncPipe, obj);
}
private _dispose(): void {
this._strategy.dispose(this._subscription!);
this._latestValue = null;
this._subscription = null;
this._obj = null;
}
private _updateLatestValue(async: any, value: Object): void {
if (async === this._obj) {
this._latestValue = value;
this._ref.markForCheck();
}
}
}